Two directions

A Piece of Mars: Sometimes I just want to show the interior of a dune field, because it’s full of waves: ripples and dune crests, slip faces, all of which signs of movement. The dunes in this 0.67×0.47 km (0.41×0.29 mi) view have been made by two winds: one blowing from the top of the frame, and a more-recently-active one blowing from the right. Together, these two winds (and gravity) push this sand between a series of hills and down into Coprates Chasma, one of the longest canyons on Mars. (HiRISE ESP_035278_1655, NASA/JPL/Univ. of Arizona)